Solar power towers are utilized to receive concentrated solar radiation to produce high-temperature thermal energy to generate utility-scale electricity or perform solar chemistry. To generate high thermal energy, solar power towers are located in fields that include numerous heliostats that collect and concentrate solar energy onto a central collector (receiver). A heliostat includes, for example, a plurality of mirrored facets on a common frame that has two axis drives, such that the heliostat can track the sun over the course of a day. Current solar power tower fields include hundreds to thousands of heliostats.
To obtain substantially optimal concentrated solar flux on the central collector from a heliostat, the individual mirrored facets are desirably canted as well as focused. With more specificity, heliostats are considered point-focus concentrators. These types of concentrators are typically tested and evaluated at the 2f position, which is at a distance that is twice the focal length away from the concentrator vertex. For heliostats that have very long slant ranges or focal lengths (hundreds of meters), however, the 2f location is not easily accessible. This makes it difficult to measure and evaluate the alignment of the heliostat facets at 2f. Accordingly, other alignment approaches have been considered.
An exemplary approach for aligning mirrored facets in a heliostat is to place the heliostat on sun while covering other heliostats in the field, and then judge the concentration of light at the solar power tower manually with the human eye. Utilizing this approach, alignment and focus of each mirrored facet in the heliostat is “tweaked” until a technician judges (qualitatively) whether a sufficient focus of flux has been achieved at the solar power tower. For solar power tower fields that include hundreds or thousands of heliostats, this approach is suboptimal due to the time required to manually align mirrored facets in all heliostats; the changing sun position affects the flux distribution, which makes it difficult to accurately judge a “good” flux distribution at the collector. Other approaches have also been considered (and implemented and/or demonstrated), but such approaches are generally relatively expensive, inaccurate, difficult to use, or too time consuming to practically implement.